Dynamically determining a tile budget when pre-fetching data in a client device

ABSTRACT

A pre-fetching map data system and method identifies a subset of map data to corresponding to one or more points of interest to be displayed on the map. The map data is stored on a remote map database in map data tiles. The pre-fetching map data system identifies those map data tiles that correspond to the one or more points of interest, where the identified pre-fetch map data tiles are sent from the remote database to a client device for cache storage. The number of pre-fetch map data tiles are determined using a tile budget that is dynamically adjusted in response to changing conditions on a client device.

CROSS-REFERENCE TO RELATED APPLICATIONS

The present application is a continuation of U.S. application Ser. No. 13/297,461 filed on Nov. 16, 2011, the disclosure of which is incorporated herein by reference in its entirety for all purposes.

FIELD OF TECHNOLOGY

The present disclosure relates to map data optimization and more specifically to a system and a method to pre-fetch map data from a remote map database.

BACKGROUND

With the widespread use of mobile devices, such as mobile phones, personal data assistants, tablet personal computers, etc., consumer demand for ready access to varied types of data continues to grow at a high rate. These devices are used to transmit, receive, and store text, voice, image, and video data. Consumers often look to store large numbers of applications on these devices, such that mobile devices are often touted more for the number of available applications, than internal processor speed. While consumers have come to desire fast access to data, the sheer amount of data required to run these applications places a premium on data management, both at the device level and at the network level. This premium limits the effectiveness of applications such as mapping applications, which typically require comparatively large amounts of network data.

Mapping applications are found in a variety of mobile devices, including car navigation systems, hand-held GPS units, mobile phones, and portable computers. These applications are among the most frequently used applications and are considered, by some, necessary for modern living. Although the underlying digital maps are easy to use from a user's perspective, creating a digital map is a data intensive process. Every digital map begins with a set of raw data corresponding to millions of streets and intersections. That raw map data is derived from a variety of sources, each providing different amounts and types of information. To effectively map a location, locate a driving route between a source and a destination, identify points of interest, etc. requires substantial amounts of data. Furthermore, many mapping applications require display of different map data at different zoom levels, i.e., different scales, where the amount of detail and that nature of that detail changes at each zoom level. For example, at a lowest zoom level, scaled farthest away from a target, the map data may contain the boundaries of continents, oceans, and major landmasses. At subsequent zoom levels that map data may identify countries, states, homelands, protectorates, other major geographic regions. While at even further subsequent zoom levels, that map data may contain major roads, cities, towns, until eventually the map data contains minor roads, buildings, down to even sidewalks and walk ways depending on the region. The amount of detail is determined by the sources of information used to construct the map data at each zoom level. But no matter the zoom level, the amount of information is voluminous and generally too large for storage, in total, on mobile devices and too large for continuous download over a wireless communication network.

In operation, mapping applications typically download map data to the mobile device through a wireless communication network and in response to a user entering a location of interest and/or based on the current location of the mobile device, such as the current global positioning satellite (GPS) data or current cellular network location data for the device. A conventional technique for downloading map data is to have the mobile device communicate this location data to a remote processor on the wireless communication network, which, in response, downloads all map data to the mobile device or the map data requested for display to the user.

Generally speaking, the map data is stored in blocks known as map data tiles, where the number of map data tiles increases with zoom level. The remote processor provides a subset of the available map data tiles for a particular location or region to the mobile device for storage and display at any particular time via a map display application. By providing large numbers of map data tiles, the mobile device may buffer the map data for display to the consumer as the consumer scrolls across an area using the mapping application looking for adjacent or other mapping locations. However, the larger the number of map tiles provided at any particular time increases the download time and buffer memory usage while the user is using the map display application.

Conventionally, map data tiles are downloaded and cached, but in a crude manner that is unable to take advantage of memory surpluses on devices and unable to take advantage of network bandwidth surpluses, e.g., when the user is not using the device. The conventional techniques are similarly deficient in the face of lacking memory and reduced bandwidth. As a result, there is a need to have more intelligent mechanisms for downloading map data, in particular map data tiles, to sufficiently satisfy the needs of the user, while doing so in a manner that addresses network bandwidth and memory conditions.

SUMMARY

In an embodiment, a computer-implemented method comprises: identifying, on a client device, one or more map points of interest; identifying, based on the map points of interest, pre-fetch map data tiles to be requested from a remote map database and stored on the client device for eventual rendering of a visual display of map data in response to a subsequent user request; requesting, from a remote map database storing the map data, the pre-fetch map data tiles corresponding to one or more map points of interest; receiving, at the client device, the pre-fetch map data tiles from the remote map database and, during receiving of the pre-fetch map data tiles; dynamically determining, at the client device, a tile budget for the client device; determining if the tile budget has been met by the received pre-fetch map data tiles, where, if the tile budget has been met, the client device stops receiving additional pre-fetch map data tiles from the map database, and if the tile budget has not been met, the client device, continues receiving additional pre-fetch map data tiles from the map database until the tile budget is met or until all pre-fetch map data tiles corresponding to the one or more map points of interest have been received at the client device; and storing the received pre-fetch map data tiles in a local memory on the client device until a subsequent user request.

In another embodiment, a computer-readable medium storing instructions, the instructions when executed by a processor cause the processor to: identify, on a client device, one or more map points of interest; identify, based on the map points of interest, pre-fetch map data tiles to be requested from a remote map database and stored on the client device for eventual rendering of a visual display of map data in response to a subsequent user request; request, from a remote map database storing the map data, the pre-fetch map data tiles corresponding to one or more map points of interest; receive, at the client device, the pre-fetch map data tiles from the remote map database and, during receiving of the pre-fetch map data tiles; dynamically determine a tile budget for the client device; determine, at the client device, if the tile budget has been met by the received pre-fetch map data tiles, where, if the tile budget has been met, the client device stops receiving additional pre-fetch map data tiles from the map database, and if the tile budget has not been met, the client device, continues receiving additional pre-fetch map data tiles from the map database until the tile budget is met or until all pre-fetch map data tiles corresponding to the one or more map points of interest have been received at the client device; and store the received pre-fetch map data tiles in a local memory on the client device until a subsequent user request.

In yet another embodiment, a computer system for fetching map tile data to be used in constructing a visual display of map data on a client device, the computer system comprises: a display module for constructing and displaying the visual display of the map data, where the map data is stored in a remote map database as a plurality of map data tiles; a map point identifier module that identifies one or more map points of interest that define pre-fetch map data tiles to be requested from a remote map database and stored on the client device for eventual rendering of a visual display of map data in response to a subsequent user request; a database interface module to request, from the map database, the pre-fetch map data tiles from the remote map database and to receive the pre-fetch map data tiles from the remote map database; and a tile budget module that, during receiving of the pre-fetch map data tiles, is to dynamically determine a tile budget and is to determine if the tile budget has been met by the received pre-fetch map data tiles, where if the tile budget has been met, the database interface module is to stop receiving additional pre-fetch map data tiles from the remote map database, and if the tile budget has not been met, the database interface module is to continue receiving additional pre-fetch map data tiles from the map database until the tile budget is met or until all pre-fetch map data tiles corresponding to the one or more map points of interest have been received at the client device. In some embodiments, the tile budget is dynamically determined by determining an available amount of map data memory allocated for the client device and setting the tile budget at or below the available amount of map data memory. In some embodiments, the tile budget is dynamically determined by updating a memory usage profile for the client device and adjusting the tile budget based on the updated memory usage profile.

In some embodiments, the tile budget is dynamically determined by determining an available number of map tile memory slots on the client device.

In some embodiments a plurality of map points of interest are identified for pre-fetching and that plurality is prioritized in order from highest to lowest, where pre-fetching occurs on the highest priority map point of interest first.

In some embodiments, the map database stores map data at different zoom levels, each containing respective sets of map data tiles, such that pre-fetching of map data tiles occurs at a plurality of the zoom levels.

The features and advantages described in this summary and the following detailed description are not all-inclusive. Many additional features and advantages will be apparent to one of ordinary skill in the art in view of the drawings, specification, and claims hereof.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is high-level block diagram of a wireless network depicting a wireless base station connected to a server containing map data for selectively communicating that map data to a various client devices on the network.

FIG. 2 is a block diagram of an example map generator in the client device of FIG. 1.

FIG. 3 illustrates a portion of the data structure for the map database of FIG. 1.

FIGS. 4A, 4B, and 4C illustrate example renditions of map data at three different zoom levels, respectively.

FIG. 5 illustrates an example process or flow diagram for identifying points of interest and map zoom levels that are used in requesting pre-fetch map data from a server and for performing a tile budget on the pre-fetch map data from the server.

FIGS. 6A, 6B, and 6C illustrate example renditions of the map data of FIGS. 4A, 4B, and 4C, at three different zoom levels, respectively, and showing points of interest at the different zoom levels.

FIG. 7 illustrates an example process or flow diagram for constructing and displaying pre-fetch map data visually.

FIG. 8 illustrates an example process or flow diagram for performing the tile budgeting of FIG. 5.

FIG. 9 illustrates an example process or flow diagram for determining points of interest to be used in identifying the pre-fetch map data.

FIG. 10 illustrates an example process or flow diagram similar to that of FIG. 5, but which ranks points of interest in priority as part of a pre-fetching map data process.

FIG. 11 illustrates an example process or flow diagram for identifying the pre-fetch map data in response to the identified points of interest, zoom levels, and tile radii.

FIG. 12 illustrates an example process or flow diagram for dynamically determining a tile budget.

FIG. 13 illustrates another example process or flow diagram for dynamically determining a tile budget.

DETAILED DESCRIPTION

The present application describes techniques for fetching map data over a selected subset of the entire map data available. The techniques, which may be implemented on a client device such as a mobile or handheld device, will access map data pertaining to these points of interest from a remote server. In this way, the techniques do not need to access an entire map database, but rather only a portion thereof. To avoid accessing too much of the map data, the techniques employ a map memory budgeting process that allows access to a threshold amount of map data.

More particularly, the present application describes techniques for fetching map data over a selected subset of the entire map data available, by identifying one or more points of interest for display on client device, where those points of interest are identified by the user of the client device, for example by the user searching for a particular location or direction between locations through a mapping application on the client device. In other embodiments, the points of interest are automatically determined by the client device, for example by the client device identifying a set of most recently accessed points of interest or a set of most frequency accessed points of interest. In either case, the points of interest are identified to a remote server that contains a map database of the entire map data, including map data for the points of interest. With the points of interest identified, the remote server begins transmitting the map data, corresponding to these points of interest, to the client device for storage and display to the user. Storing map data in data blocks known as map data “tiles,” the remote server sends the map data in the form of a map data tiles. For each point of interest, the server may send an identified set of map data tiles, termed pre-fetch map data tiles. The client device receives the pre-fetch map data tiles until a tile budget has been met, which the client device may assess upon receipt of each map data tile sent from the server or which it may assess periodically, for example, after receipt of any subset of map data tiles sent from the server. The client device continues receiving map data tiles until the tile budget is met. In some embodiments, the client device prioritizes the points of interest and requests and receives map data tiles in an order according to these priorities. If the client device receives all of the pre-fetch map data tiles for the highest priority point of interest, then the client device starts requesting and receiving the pre-fetch map data tiles for the next highest priority point of interest, which the client device keeps doing until a tile budget has been met. The tile budget may be a fixed number of map tiles or it map be a total mount of map data that is to be stored on the client device.

Pre-fetching refers to requesting map data from a remote map database, such as that of a remote server, prior to any specific user request for map data, so that map data may be collected and buffered on a device until a specific user request for map data. In this way, pre-fetching seeks to collect map data in the background, before that map data is called upon to construct a visual display, thereby reducing (and even eliminating) the need for a client device to request map data only after a user request. The pre-fetched map data is automatically identified, requested, and stored on the client device for subsequent use in constructing a visual display. As discussed in examples below, where that map data is stored in the remote map database in the form of map data tiles, the pre-fetching is of map data tiles.

FIG. 1 is a high-level block diagram that illustrates a computing environment for a pre-fetch map data system 100 that may be used to access and store map data within a map database. As illustrated in FIG. 1, the computing environment includes a map database 103 connected to or disposed within a server 105, which is, in turn, connected to a number of client devices 115 through a network 125. The network 125 includes but is not limited to any combination of a LAN, a MAN, a WAN, a mobile, a wired or wireless network, a private network, or a virtual private network. While only three clients 115 are illustrated in FIG. 1 to simplify and clarify the description, it is understood that any number of client computers are supported and can be in communication with the server 105.

Both the server 105 and the clients 115 are computers that may include a CPU 130 (only shown in the clients), one or more computer readable memories 132, one or more user interfaces 134 (keyboard, touch screen, etc.), a network interface 136, one or more peripheral interfaces, and other well known components. As is known to one skilled in the art, other types of computers can be used that have different architectures. The client devices 115 represent any suitable handheld and/or mobile device, such as a mobile phone, personal data assistant, laptop computer, tablet personal computer, car navigation system, hand-held GPS unit, or “smart” device. More broadly, the client devices 115 represent any personal computing device, database, server, or network of such devices, or any other processing device having a user interface and CPU and capable of displaying a visual rendition of map data accessed from the map database 103 or other remote source of map data. Furthermore, while in some examples, the network 125 is described as a wireless network, the network 125 may be any wired or wireless network, where the clients 115 are devices on the network.

The server 105 and the clients 115 are also adapted to execute computer program modules for providing functionality described herein. As used herein, the terms “module” and “routine” refer to computer program logic used to provide the specified functionality. Thus, a module or a routine can be implemented in hardware, firmware, and/or software. In one embodiment, program modules and routines are stored on a storage device, loaded into memory, and executed by a processor or can be provided from computer program products that are stored in tangible computer-readable storage mediums (e.g., RAM, hard disk, optical/magnetic media, etc.).

The map database 103, which may be stored in or may be separate from the server 105, contains map data that can be used to generate a digital map or that can be used by, for example, a navigation system to determine routes between two locations. Physical roads, waterways, parks, landmarks, and other geographic elements may be represented in the map data by a list of nodes and segments that connect those nodes. Each node corresponds to a specific geographic location in the physical world. The data representation for each node generally includes a set of coordinates (e.g., latitude and longitude) and an association with one or more segments. For roads, each segment corresponds to a section of a physical location that begins at one node and ends at a different node. The data representation for each road segment, for example, can include a length and a number of attributes, such as a street name, a priority (e.g., a highway or a local road), speed information, a surface type, a road width, an indication of whether the road segment is a one-way segment, address ranges, usage (e.g., ramp or trail), etc.

The map data stored in the map database 103 can be obtained from several different sources such as the New York City Open Accessible Space Information System (OASIS) and the U.S. Census Bureau Topologically Integrated Geographic Encoding and Referencing system (TIGER). The map data can also be accessed by one of the map generators 120, modified, and stored back into the database 103. Further, the database 103 does not need to be physically located within server 105. For example, the database 103 can be partially stored within a client 115, can be stored in external storage attached to the server 105, or can be stored in a network attached storage. Additionally, there may be multiple servers 105 that connect to a single database 103. Likewise, the map database 103 may be stored in multiple different or separate physical data storage devices.

Each client 115 executes one of the map generators 120, each of which receives pre-fetch map data from the server 105 and generates a visual display of the received map data that is presented to the user on a display of the interface 134. The map generator 120 is able to adjust that visual display in response to user interactions with the interface 134, for example, adjusting which map data is visualized at any given time in response to a user selecting to scroll (left, right, up, down, etc.) through the visual display, or in response to the user selecting to change the zoom level (e.g., scale) of the displayed map data.

As illustrated in the detailed example of FIG. 2, the client 115 may include various modules within or associated with the map generator 120, including a database interface module 181 that operates to retrieve map data from the server 105 and map database 103. The map generator 120 further includes a map point identifier module 182 capable of identifying one or more points of interest that are to be used by a display module 184 to create a visual map display of received map data on the interface 134. The points of interest are communicated by the interface module 181 through the network interface 136 through network 125 to the server 105, which responds by sending pre-fetch map data from the map database 103 back to the client device 115, where this pre-fetch map data is received by the database interface module 181 and stored in a map buffer memory 180 of the client 115. A map data selection module 186 accesses the stored pre-fetch map data and determines which portion of that buffered map data is to be provided to the display module 184 for creating the visual map display on the interface 134. The module 186, therefore, is responsive (after pre-fetching) to user interaction with the interface 134 to determine which portion of the pre-fetched map data should be displayed to the desires in response to a subsequent user interaction, which is determined by a centralized map position, user scrolling, and zoom level, for example.

In the illustrated embodiment, the map generator 120 further includes a tile budget module 188 that limits the amount of pre-fetch map data tiles that can be received to the client device. The client 115, for example, receives map data tiles at the database interface module, where upon receipt of one or any predetermined number of map data tiles the tile budget module 188 determines if the client device 115 has received a sufficient, or maximum amount of map data tiles, at which point the tile budget module 188 instructs the database interface module 181 to stop requesting and storing additional map data tiles. The tile budget module additionally determines the tile budget during receipt of pre-fetch map data tiles, which allows the map generator 120 to apply a dynamically changing tile budget policy capable of adapting to changing resource conditions on the client device 115.

While the tile budget module 188 is described as contained within the map generator 120, in other examples, a tile budget module may be stored in the server 105 or in both the client 115 and the server 105. The tile budget module 188, for example, may be implemented in the map generator 120 of the client 115 or implemented as a standalone or integrated module at the server 105. In some embodiments, the database interface module 181 receives zoom level data from a zoom level module 190, which identifies at what zoom level the module 181 is to request pre-fetch map data tiles. In this way, the client device 115 may receive pre-fetch map data at one or more zoom levels to store in the buffer memory 180.

Of course, some embodiments of the map generator 120 may have different and/or other modules than the ones described herein. Similarly, the functions described herein can be distributed among the modules in accordance with other embodiments in a different manner than that described herein.

Generally speaking, map data in the map database 103 is stored in different zoom levels each formed of a plurality of map data blocks, termed map tiles, which are used to construct a visual display of the map. FIG. 3 illustrates an example data structure 200 of a portion of the map database 103. The map data is stored in numerous (n) different zoom level data structures (only three of which are shown) 202A, 202B, and 202C, where each data structure is formed by a plurality of map data tiles. The data structure 202B, which is the only one numbered for explanation purposes, shows the map data at zoom level, z=2, is formed of 18 map data tiles, 204A-204R. The map tiles represent the basic building blocks for constructing a map display. Each map tile contains necessary map data to construct a portion of the map display, including data identifying roads, buildings, and geographic boundaries, such as water lines, county lines, city boundaries, state lines, mountains, parks, etc. The map data may be stored in any number of different zoom level data structures. In an embodiment, 19 total zoom levels are stored in the map database 103.

The number of tiles at each zoom level increases, e.g., linearly, quadratically, exponentially, or otherwise. The zoom levels in the illustrated example (z=1, 2, and 5) have 6, 18, and 60 map data tiles, respectively, covering the same geographic area or region.

In some embodiments, each map tile contains map data stored in a bitmap format, for display to the user using a raster display engine executed by the display module 184. In other embodiments, the map tile may contain map data stored in vector format, for display using a vector buildup display engine executed by the display module 184. In either case, the display module 184 may employ a C++, HTML, XML, JAVA, or Visual Basic application for generating a visual display of the map tiles.

In the illustrated embodiment, all map data is stored in map tiles, and each map tile in a zoom level data structure is allocated the same memory allocation size. For example, each tile 204A-204R may be a bitmap image 10 Kbytes in size. This may be achieved, for example, by having each map tile cover the same sized geographic area. For map tiles containing vector data, the data size for each tile may vary, but each tile may still, in some embodiments, be allotted the same maximum memory space. Although not illustrated, in other embodiments, the data tiles will have different memory space allocations within a zoom level data structure.

FIGS. 4A-4C illustrate visual map displays, e.g., that may be fully or partially displayed on the user interface 134, where each figure provides a visual display at a different zoom level. In the illustrated embodiments, FIG. 4A provides a visual map display 300 at an example zoom level, z=6, constructed of a series of map tiles 302-318, which cover the same size geographic area and which have the same amount of memory size.

In operation, the server 105 is able to transmit map data to respective clients 115 in chunks of data defined by these map tiles. For example, to transmit the map data needed to construct the map display 300, the server 105 may transmit each map tile in a frame, having a header portion providing identification data of the frame (such as geographic position, client device address, map tile version number, etc.) and a payload portion containing the specific map tile data to be used in forming the visual display. Map data tiles provide an effective mechanism for quantizing map data stored in the map database 103 and for quantizing communication of the map data over the network 125 to the clients 115.

In comparison to FIG. 4A, FIG. 4B illustrates a visual map display 400 at a zoom level higher than the zoom level of FIG. 4A, in this example zoom level, z=10. The map display 400 is formed of a plurality of map tiles 402-432. Like the map tiles 302-318, the map tiles 402-432 are each the same in size, e.g., covering the same geographic area and having the same memory size. FIG. 4C illustrates another visual map display 500 at a third even higher zoom level, zoom level z=12, formed of map data tiles.

Each of the displays 300, 400, and 500 is of a portion of the overall map data, which comprises many more map data tiles.

As illustrated across FIGS. 4A-4C, the map tiles that form each visual map display have various levels of detail. The tiles 302-318 illustrate geographic boundaries, but no roads, only highways and/or interstates, while the tiles of FIG. 4C are at a higher zoom level and contain information on roads, buildings, parks, end points, etc.

As the zoom levels increase, i.e., as the visual map display focuses down on a smaller geographic region, the amount of map data may reach a maximum point, beyond which all zoom levels will contain the same map data. The number of map tiles needed to construct a map display may vary but the total amount of map data becomes saturated. The zoom level corresponding to this point is termed the saturation zoom level and represents the zoom level at which all roads, building, parks, end points, and other map data elements for a geographic region are provided. Any additional zoom levels selected by the user merely zoom in further on these map data elements. In the illustrated example of FIGS. 4A-4C, zoom level, z=12, represents the saturation zoom level.

While a user interacts with the visual map displays 300, 400, and 500, the user may wish to scroll around to display other map data near the illustrated map data. Therefore, the client device 115 uses a system to fetch and store a sufficient amount of map data to form the visual map display while buffering additional map data at the local device 115 to allow efficient user interaction with that display.

FIG. 5 illustrates a routine or process 700 for requesting and receiving map data tiles from a remote server. At a block 701, the routine or process 700 awaits initiation, which may result from user action, such as a user activating a mapping application on the client device 115. Initiation may also result from user or application initiated searches, direction end points, and stored location accesses by a user or application. In some embodiments, the block 701 functions to automatically initiate the routine or process 700, for example, by periodically initiating pre-fetching map data. The block 701 may be designed to initiate the process every hour, every day, a few times a day, or at any other suitable periodic interval. In some embodiments, that automatic initiation can occur in response to an event unbeknownst to the user of the client device, such as when mobile wireless services are initially activated on the client device, when the client device enters entirely new geographic region, such as when a user has traveled to a city location.

At a block 702, the map point identification module 182 automatically (i.e., without user interaction or initiation) determines one or more map points of interest to display to a user via the interface 134. The module 182 may automatically identify points of interest, for example, by determining a GPS position of the current location of the client 115, by determining most recently searched points of interest, by accessing a database of stored points of interest, or by determining the most recently visited points of interest (e.g., cities, neighborhoods, etc.). Of course, in some of these cases, the module 182 may determine locations for which to download map data for storage at the user device as a background application and thus without any particular user interaction. An example further implementation of the module 182 and the block 702 is described in the routine or process of FIG. 8.

In other examples, the module 182 may manually determine the points of interest based on previous user input, for example, through the user providing an address into a data field presented on the interface 134, or through the user selecting to find a point of interest obtained through interaction with the interface 134 more generally. For example, the user can access a web-browser or other program running on the client device that identifies a location, business, home, etc., from which the module 182 may allow the user to select such item for building a map display of the vicinity around such point of interest. Any suitable manual method for entering or otherwise identifying one or more points of interest may be used by module 182 and collected by the block 702. Further still, these manual methods can be modified into automatic methods of map point identification, by having the block 702 access historical data on previous, manual user data inputs.

FIGS. 6A-6C illustrate the visual map displays (300, 400, and 500) of FIGS. 4A-4C, respectively, but showing map points of interest identified by the module 182. The points of interest that are displayed on the user interface 134 depending on the zoom level. FIG. 6A illustrates three points of interest 602, 604, and 606; while FIG. 6B illustrates only two points of interest 604 and 606; and FIG. 6C illustrates only one point of interest 606.

For convenience purposes the remainder of the routine or process 700 will be described in terms of a single map point of interest being identified by the block 702. It will be understood, that the same blocks would be executed if multiple map points of interest were identified.

Returning to FIG. 5, at a block 704, one or more desired zoom levels are identified (by map zoom module 190). If the routine or process 700 is initiated by the user interacting with a map application, the zoom level module 190 may identify a zoom level based on the zoom level selected by the user. In other embodiments, the zoom level module 190 may identify the most recently last used zoom level by the user or the most frequently used zoom level as the identified zoom level.

At a block 706, the database interface module 181 communicates the map points of interest (block 702) and the zoom level data (block 704) to the server 105, in particular, in the illustrated embodiment, to a pre-fetch module 750 at the server 105 (see, FIG. 1). The pre-fetch data engine 750 then identifies the one or more map points of interest and zoom level(s) and determines the map data corresponding to the one or more points of interest at the selected one or more zoom levels that are to be fetched from the map database 103. The engine 750 collects the corresponding map tiles and begins transmitting that map data to the map generator 120.

In the illustrated embodiment, at the block 706, the database interface module 181 requests pre-fetch map data for all map points of interest at one time, for example, by sending to the server a data frame having an identification header that contains, among other things, an identification field identifying the client device and having a payload that identifies the one or more map points of interest and the zoom level or zoom levels for which to collect map data. The map points of interest may be identified by a longitude and latitude coordinate, in some embodiments. Optionally, in some embodiments where the block 706 requests all pre-fetch map data at once, the server 105 may send the responsive pre-fetch map data tiles in subsets, i.e., in blocks of one or more map data tiles, but not in a continuous stream. As each subset of the pre-fetch map data tiles is received, the block 706 may send a return signal, in the form of an “acknowledgment” signal, back to the server 105 to confirm receipt of the data.

The map data tiles are received at a block 708 (database interface module 181), after which at a block 709 the tile budget module 188 dynamically determines the tile budget for the client device 115. Example implementations of the block 709 are discussed in detail below in regards to FIGS. 12 and 13. In general, through the block 709, the tile budget module 188 is able to adjust the tile budget in response to changing conditions on the client device 115. In this way, a fixed or predetermined tile budget value is replaced with a dynamic value that is capable of changing during receipt of pre-fetch map data. The changing conditions can be on memory usage in the client device.

Generally, the amount of memory made available for map data, i.e., the map data memory, may be set on the device. Typically, the total amount device memory available for map data will be set well below the total device memory. When a user is running multiple, simultaneous applications on the client device, however, the overall memory available for cache by these applications may change. Therefore, in some examples, the total amount of allocated map data memory may be adjusted upward or downward, e.g., depending on operating conditions of the device or in changes to the device physical memory, such as when a customer adds physical memory to a device, such as a secure digital (SD) memory card to device. Through the block 709 such changes may be identified and used in setting the tile budget at any given time, before, during or after receipt of pre-fetch map data tiles. The available map data memory may be general memory on the client device 115 or a dedicated memory for map specific data, whether that memory is a physically separate memory or a dedicated virtual portion of a general storage memory on the client device 115.

At the block 709, the tile budget module 188 also performs a tile budget check on the received map data tiles to determine if a tile budget has been met. If the tile budget has not been met, then the client device 115 stores that pre-fetch map data through a block 710 (database interface module 181), in the memory buffer 180. At a block 712, the routine or process 700 determines whether all pre-fetch map data tiles have been received to the client device 115. If not, then control is passed to block 708 to receive further map data tiles. Optionally in some embodiments control is passed to the block 706, which transmits a “continuing request” signal that instructs to the server 115 to send the next subset of pre-fetch map data tiles. If there are no further map data tiles to received from the server, the routine or process 700 passes control to a block 713, where the client device 115 awaits some user interaction, i.e., a subsequent interaction after the pre-fetching of blocks 701-710. Once as user as performed an interaction that is to result in rendering (i.e., construction and display) of a visual map display, through a block 714, the module 186 identifies a subset of the previously-stored pre-fetch map data to display to the user on a visual display that is rendered by the display module 184 through a block 716.

If the tile budget check at the block 709 identifies that a tile budget will be met by the received map data tile(s), the received map data tile(s) will be stored, if memory allows, by a block 718, and control is passed to the block 713. This step prevents further map data tiles from being received and stored on the client device 115. Optionally, in some embodiments, upon a tile budget being met, the database interface module 181 is instructed to transmit a “stop” instruction signal to the server, which the server then interprets and stops from sending any further map data tiles.

FIG. 7 illustrates a routine or process 800 that may be performed by the blocks 714-716 (display module 184), i.e., in response to a user request for map data occurring after the pre-fetch map data has been automatically collected and stored. The client device 115 maintains all received pre-fetch map data from the server 105 in the memory buffer 180. A block 802 identifies an initial subset of the pre-fetch map data; and a block 804 constructs and displays on the user interface 134 a visual map display of this initial subset of the pre-fetch map data, including one or more map points of interest. The initial display is provided to visual the map points of interest. The display is initial in that the client device will have likely received and stored a large number of map data tiles, too many to display at any given time, irrespective of zoom level. At a block 806, the routine or process 700 detects further user interactions with the interface 134, waiting the user to interact with the visual display of map data as the user selects different regions of the map data that are to be displayed. For example, the block 806 detects a user scrolling across the displayed map data to depict adjacent map data to the initial point of interest. Such scrolling may be sideways across the display, up or down, or any other desired direction. The user may also choose to alter the map by changing zoom levels, either increasing to zoom in further on the map data or decreasing to zoom further out. The block 806 identifies map manipulation user interaction data to the block 802, which then determines which other pre-fetched map data, stored in the buffer memory 180, is to be displayed in response to the user interaction. Or the block 806, upon appropriate instruction from the user, terminates the routine or process 800 entirely, for example, when a user selects to exit a mapping application.

FIG. 8 illustrates a routine or process 900 that may be implemented by the block 709 (the tile budget module 188). A process 902 analyzes the subset of pre-fetch map data tiles received from the server 105, where in the illustrated example such analysis includes incrementing a total number of map data tiles received and determining a total amount of map data (measured in kilobytes, megabytes, or gigabytes) received from the server 105. At a block 904, tile budget module 188 identifies a first tile budget criterion. The module 188 may use any number of tile budget criteria. The illustrated example is described with respect to two tile budget criteria: a total number of received map data tiles and a total amount of map data. The block 904 initially identifies the total number of received map data tiles, in the discussed embodiment. A block 906 determines if the tile budget has been met by the received subset of pre-fetch map data tiles, i.e., whether the number of received map data tiles exceeds a threshold number of data tiles stored in the memory 132 of the client device 115. If the first tile budget criterion is not met, a block 908 determines if there are additional tile budget criteria. If there are, control is passed back to the block 904, which identifies the next tile budget criterion and the steps repeat. Once there are no further tile budget criterion, at a block 910 control is passed back to block 708.

Upon the various tile budget criteria checks of block 906, if it is determined that the tile budget has been met, a block 912 sends a “stop” instruction to the server 115 (through the database interface module 181) to instruct the server to stop sending any additional pre-fetching map data tiles. The block 912 instructs that control be passed to the block 714 for storing the received pre-fetch map data tiles, if there is sufficient memory for storing the tiles. If there is not, the received pre-fetch map data tiles exceeding the tile budget are discarded.

FIG. 9 illustrates a routine or process 1000 for automatically (prior to user interaction or initiation) determining points of interest as may be used by block 702. The map point identifier module 182 performs a series of data polling operations, accessing data stored in the memory 132 to aggregate one or more potential points of interest. At a block 1002, the module 182 polls current user interaction data or stored user map interaction data, such as data on past user interactions with map data displayed on the interface 134, including data such as locations highlighted by the user, map points placed on a map display by the user, and geographic regions most displayed on a map display, for example. At a block 1004, the module 182 polls data on user searches, identifying locations the user has requested be identified on a map display. At a block 1006, the module 182 polls any other location data, including current geographic position and stored geographic position. The latter can include data that tracks geographic position of the client device 115 to automatically determine location patterns. For example, the module 182 may collect data on client device location during the traditional workweek, Monday-Friday, and use that data for pre-fetching map data corresponding to typical travel patterns of the client device. The module 182 may collect different data to determine different typical travel patterns, and thus different potential points of interest, during the weekend. It is noted that these examples are described in terms of points of interest, but as used herein, a point of interest represents a particular point on a map or any region of a map that can be defined (specifically or even generally) by a map point.

At a block 1008, the module 182 aggregates the polled potential points of interest data and provides this data to a block 1010 which determines a set of one or more points of interest to be used by block 704 to determine the corresponding one or more tile radii. The block 1010 may determine the points of interest by using a threshold, for example, identifying any points of interest that have been accessed by the user a certain number of times or a certain percentage of time over a given period of time. The block 1010 may determine the points of interest comparatively, for example, by determining which points of interest are the most frequently accessed. The block 1010 may make the determination based on which points of interest are most recently accessed.

FIG. 10 illustrates a routine or process 1100 similar to that of FIG. 5, but in which a plurality of map points are identified and ranked in a priority order that is used to determine the order in which the client device 115 requests pre-fetch map data from the server 105. At a block 1101, the routine or process 1100 awaits initiation, in a similar manner to that of block 701 in FIG. 5. At a block 1102, the module 182 identifies a plurality of map points of interest, for example, performing similar operations to that of block 702 described above, namely, determining the map points of interest based on manual input from a user as well as automatically identifying map points of interest, from a current location of the client 115, most recently searched points of interest, stored points of interest, and/or most recently visited points of interest. At a block 1104, the module 190 identifies a desired zoom level or zoom levels for each of the map points of interest.

At a block 1105, the map point identifier module 182 performs a prioritization on the identified map points of interest, ranking them in order of priority from a highest to a lowest. The block 1105 then identifies a highest priority map point of interest, which a block 1106 (module 181) identifies to the server, more specifically to a pre-fetch data engine (not shown). A block 1108 (module 181) receives a subset of the pre-fetch map data tiles from the server. At a block 1109, the tile budget module 188 determines the tile budget and then performs tile budget checking, similar to that of the block 709 described above. A block 1110 stores the received pre-fetch map data tiles if the tile budget has not been met. If the tile budget has been met, then a block 1111 stores the received pre-fetch map data tiles, if possible, and passes control to a block 1113, where the client device awaits user interaction like block 713 of FIG. 5, after which at a block 1115, the module 186 identifies tiles among the stored pre-fetch map data tiles that are to be used by module 184 (block 1116) for rendering a visual display of the map data.

At a block 1112, the routine or process 1100, determines whether there are additional pre-fetch map data tiles corresponding to the highest priority map point of interest. If so, control is passed back to block 1108 for receiving additional subsets of the pre-fetch map data tiles (or optionally block 1106) and then to block 1109 for performing tile budget checking. These additional pre-fetch map data tiles may be those of different zoom levels for the highest priority map point of interest, data tiles associated with areas around or adjacent to the highest priority map point of interest, etc. If not, then all pre-fetch map data tiles for the first map point of interest have been received and stored, and the routine or process 1100 passes control to a block 1114 which determines if there is at least one additional map point of interest. If so, control is passed to the block 1105 which identifies the next highest priority map point of interest and communicates the same to the block 1106 which then requests pre-fetch map data tiles corresponding to that next highest priority map point of interest. This process continues until pre-fetch map data tiles for all map points of interest have been downloaded or until the tile budget has been met. If there are no additional map points of interest, the block 1114 passes control to the block 1113.

FIG. 11 illustrates an example routine or process 1200 as may be performed by the server 105, specifically the pre-fetch data engine 750, upon receipt of the identified points of interest and zoom levels at a block 1202. At a block 1204, the server 105 accesses the map database 103, and takes one of the points of interest and identifies the map data corresponding to that point of interest, at a block 1206. A block 1208 identifies a zoom level, e.g., from the zoom level received to block 1202, at which to collect the initial set of map data from the database 103. For the identified zoom level, a block 1210 identifies the first point of interest collects all map data tiles the correspond to the point of interest, which thereby identifies the pre-fetch map data associated with that point of interest. For example, if each tile in the map data is stored with an assigned position value relative to the other tiles, such as an assigned longitude value and an assigned latitude value or an assigned column value and an assigned row value, then the block 1210 may identify a pre-determined set of map data tiles adjacent the map data tile containing the point of interest.

At a block 1212, the server 105 transmits a subset of the identified pre-fetch map data tiles collected at block 1210 to the requesting client device 115, where the requesting client device 115 is identified by address information in a header of the data provided to block 1202. The server sends a subset of the pre-fetch map data tiles, which allows the client device 115 to frequently perform tile budgeting checks on the received data. The subset includes at least one pre-fetch map data tile; and the smaller the subset the more frequently the client device 115 will check for whether the tile budget has been reached.

In the illustrated embodiment, at a block 1214, the server 105 determines if the client device has identified a need for map data stored at additional zoom levels, where if so, control is passed back to the block 1208 which identifies the next zoom level and the process repeats, as described. In some embodiments, the client device 115 (i.e., the database interface module 181 via block 706), sends requests for pre-fetch map data on a per point of interest basis, i.e., awaiting receipt of all pre-fetch map data tiles for one point of interest, before identifying the next point of interest to the server 105. In other embodiments, the client device 115 (again through block 706) requests pre-fetch map data for a plurality of map points of interest at one time. In the case of the later, if no additional zoom level data is required for the particular point of interest, then a block 1216 determines if additional points of interest have been identified by the client device, where if so, control is passed back to the block 1206 which identifies the next point of interest and the process repeats, as described. If not the routine or process 1200 ends.

FIG. 12 illustrates an example routine or process 1300 for dynamically determining the tile budget, as may be implemented by block 709 or 1109. A block 1302 awaits identification that a subset of pre-fetch map data tiles have been received to the client device. In response to receipt of the map data tiles, at a block 1304, the tile budget module 188 determines the amount of available map data memory allocated on the client device. This allocated map data memory can be previously determined or determined by the block 1304 based on a set of metrics or a formulation and is set to be considerably less than the total available device memory. In an embodiment, the module 188 accesses a general purpose memory 1306 on a client device and determines available memory space. In another embodiment, the module 188 accesses a map data specific memory 1308, which is a portion of the memory 1306 allocated specifically to storing map data, in the illustrated example. In either case, the block 1304 determines the amount of available map data memory at the time of inspection, either the size of the memory 1306 or the allocated or available portion of the memory 1308. At a block 1310, the routine or process 1300 accesses the current tile budget settings for the various tile budget criteria and analyzes these in light of the determined available amount of memory. At a block 1312, it is determined whether any of the tile budget criteria are to change in light of the conditions on the client device. At a block 1314, any identified tile budget criteria to be changed is changed, or otherwise the routine or process 1300 ends without changing any tile budget criteria. For example, the block 1312 may identify that the amount of map data memory available for storage of pre-fetch map data tiles needs to be changed; and block 1314 performs that change. In the illustrated embodiment, any of the tile budget criteria will be updated via block 1314. The analysis of blocks 1310 and 1312 may determine that all or fewer than all tile budget criteria are to change. In some examples, one tile budget may require updating based on measured conditions on the client device, while another tile budget may not.

FIG. 13 illustrates a routine or process 1400, similar to that of 1300, which may be used in another embodiment to dynamically determine the tile budget, e.g., to be performed at block 709 or block 1109. Blocks 1402 and 1404 are similar to blocks discussed in FIG. 14. The routine or process 1400 differs with respect to block 1406, where a map data tile memory allocation size is accessed, and block 1408, where it is determined the number of map tile memory slots available on the client device. At a block 1406, the routine or process 1400 accesses a current tile memory slot allocation size. In the illustrated embodiment, a memory 1410 on the client device has a dedicated map buffer memory 1412, which is partitioned into tile memory slots, which are memory blocks the same size as a map data tile. For example, when the map buffer memory 1412 is allocated 20 tile memory slots, then 20 map data tiles from server 105 may be stored on the client device before the tile budget is met. In any event, the size of the buffer memory 1412 may change during operation of the client device, e.g., to respond to changing resources running on the client device and changes in memory usage. At the block 1408, the number of available tile memory slots is re-determined based on the current amount of available memory and the current amount of tile memory allocation size.

If it is determined that the tile budget has changed, i.e., if the number of available time memory slots has changed, then a block 1414 passes control to a block 1416 which updates the corresponding tile budget criterion, otherwise the process ends.

Throughout this specification, plural instances may implement components, operations, or structures described as a single instance. Although individual operations of one or more methods are illustrated and described as separate operations, one or more of the individual operations may be performed concurrently, and nothing requires that the operations be performed in the order illustrated. Structures and functionality presented as separate components in example configurations may be implemented as a combined structure or component. Similarly, structures and functionality presented as a single component may be implemented as separate components. These and other variations, modifications, additions, and improvements fall within the scope of the subject matter herein.

For example, the network 125 may include but is not limited to any combination of a LAN, a MAN, a WAN, a mobile, a wired or wireless network, a private network, or a virtual private network. Moreover, while only three clients 115 are illustrated in FIG. 1 to simplify and clarify the description, it is understood that any number of client computers are supported and can be in communication with the server 105.

Additionally, certain embodiments are described herein as including logic or a number of components, modules, or mechanisms. Modules may constitute either software modules (e.g., code embodied on a machine-readable medium or in a transmission signal) or hardware modules. A hardware module is tangible unit capable of performing certain operations and may be configured or arranged in a certain manner. In example embodiments, one or more computer systems (e.g., a standalone, client or server computer system) or one or more hardware modules of a computer system (e.g., a processor or a group of processors) may be configured by software (e.g., an application or application portion) as a hardware module that operates to perform certain operations as described herein.

In various embodiments, a hardware module may be implemented mechanically or electronically. For example, a hardware module may comprise dedicated circuitry or logic that is permanently configured (e.g., as a special-purpose processor, such as a field programmable gate array (FPGA) or an application-specific integrated circuit (ASIC)) to perform certain operations. A hardware module may also comprise programmable logic or circuitry (e.g., as encompassed within a general-purpose processor or other programmable processor) that is temporarily configured by software to perform certain operations. It will be appreciated that the decision to implement a hardware module mechanically, in dedicated and permanently configured circuitry, or in temporarily configured circuitry (e.g., configured by software) may be driven by cost and time considerations.

Accordingly, the term “hardware module” should be understood to encompass a tangible entity, be that an entity that is physically constructed, permanently configured (e.g., hardwired), or temporarily configured (e.g., programmed) to operate in a certain manner or to perform certain operations described herein. As used herein, “hardware-implemented module” refers to a hardware module. Considering embodiments in which hardware modules are temporarily configured (e.g., programmed), each of the hardware modules need not be configured or instantiated at any one instance in time. For example, where the hardware modules comprise a general-purpose processor configured using software, the general-purpose processor may be configured as respective different hardware modules at different times. Software may accordingly configure a processor, for example, to constitute a particular hardware module at one instance of time and to constitute a different hardware module at a different instance of time.

Hardware modules can provide information to, and receive information from, other hardware modules. Accordingly, the described hardware modules may be regarded as being communicatively coupled. Where multiple of such hardware modules exist contemporaneously, communications may be achieved through signal transmission (e.g., over appropriate circuits and buses) that connect the hardware modules. In embodiments in which multiple hardware modules are configured or instantiated at different times, communications between such hardware modules may be achieved, for example, through the storage and retrieval of information in memory structures to which the multiple hardware modules have access. For example, one hardware module may perform an operation and store the output of that operation in a memory device to which it is communicatively coupled. A further hardware module may then, at a later time, access the memory device to retrieve and process the stored output. Hardware modules may also initiate communications with input or output devices, and can operate on a resource (e.g., a collection of information).

The various operations of example methods described herein may be performed, at least partially, by one or more processors that are temporarily configured (e.g., by software) or permanently configured to perform the relevant operations. Whether temporarily or permanently configured, such processors may constitute processor-implemented modules that operate to perform one or more operations or functions. The modules referred to herein may, in some example embodiments, comprise processor-implemented modules.

Similarly, the methods or routines described herein may be at least partially processor-implemented. For example, at least some of the operations of a method may be performed by one or processors or processor-implemented hardware modules. The performance of certain of the operations may be distributed among the one or more processors, not only residing within a single machine, but deployed across a number of machines. In some example embodiments, the processor or processors may be located in a single location (e.g., within a home environment, an office environment or as a server farm), while in other embodiments the processors may be distributed across a number of locations.

The one or more processors may also operate to support performance of the relevant operations in a “cloud computing” environment or as a “software as a service” (SaaS). For example, at least some of the operations may be performed by a group of computers (as examples of machines including processors), these operations being accessible via a network (e.g., the Internet) and via one or more appropriate interfaces (e.g., application program interfaces (APIs).)

The performance of certain of the operations may be distributed among the one or more processors, not only residing within a single machine, but deployed across a number of machines. In some example embodiments, the one or more processors or processor-implemented modules may be located in a single geographic location (e.g., within a home environment, an office environment, or a server farm). In other example embodiments, the one or more processors or processor-implemented modules may be distributed across a number of geographic locations.

Some portions of this specification are presented in terms of algorithms or symbolic representations of operations on data stored as bits or binary digital signals within a machine memory (e.g., a computer memory). These algorithms or symbolic representations are examples of techniques used by those of ordinary skill in the data processing arts to convey the substance of their work to others skilled in the art. As used herein, an “algorithm” is a self-consistent sequence of operations or similar processing leading to a desired result. In this context, algorithms and operations involve physical manipulation of physical quantities. Typically, but not necessarily, such quantities may take the form of electrical, magnetic, or optical signals capable of being stored, accessed, transferred, combined, compared, or otherwise manipulated by a machine. It is convenient at times, principally for reasons of common usage, to refer to such signals using words such as “data,” “content,” “bits,” “values,” “elements,” “symbols,” “characters,” “terms,” “numbers,” “numerals,” or the like. These words, however, are merely convenient labels and are to be associated with appropriate physical quantities.

Unless specifically stated otherwise, discussions herein using words such as “processing,” “computing,” “calculating,” “determining,” “presenting,” “displaying,” or the like may refer to actions or processes of a machine (e.g., a computer) that manipulates or transforms data represented as physical (e.g., electronic, magnetic, or optical) quantities within one or more memories (e.g., volatile memory, non-volatile memory, or a combination thereof), registers, or other machine components that receive, store, transmit, or display information.

As used herein any reference to “one embodiment” or “an embodiment” means that a particular element, feature, structure, or characteristic described in connection with the embodiment is included in at least one embodiment. The appearances of the phrase “in one embodiment” in various places in the specification are not necessarily all referring to the same embodiment.

Some embodiments may be described using the expression “coupled” and “connected” along with their derivatives. For example, some embodiments may be described using the term “coupled” to indicate that two or more elements are in direct physical or electrical contact. The term “coupled,” however, may also mean that two or more elements are not in direct contact with each other, but yet still co-operate or interact with each other. The embodiments are not limited in this context.

As used herein, the terms “comprises,” “comprising,” “includes,” “including,” “has,” “having” or any other variation thereof, are intended to cover a non-exclusive inclusion. For example, a process, method, article, or apparatus that comprises a list of elements is not necessarily limited to only those elements but may include other elements not expressly listed or inherent to such process, method, article, or apparatus. Further, unless expressly stated to the contrary, “or” refers to an inclusive or and not to an exclusive or. For example, a condition A or B is satisfied by any one of the following: A is true (or present) and B is false (or not present), A is false (or not present) and B is true (or present), and both A and B are true (or present).

In addition, use of the “a” or “an” are employed to describe elements and components of the embodiments herein. This is done merely for convenience and to give a general sense of the description. This description should be read to include one or at least one and the singular also includes the plural unless it is obvious that it is meant otherwise.

Still further, the figures depict preferred embodiments of a map editor system for purposes of illustration only. One skilled in the art will readily recognize from the following discussion that alternative embodiments of the structures and methods illustrated herein may be employed without departing from the principles described herein

Upon reading this disclosure, those of skill in the art will appreciate still additional alternative structural and functional designs for a system and a process for identifying terminal road segments through the disclosed principles herein. Thus, while particular embodiments and applications have been illustrated and described, it is to be understood that the disclosed embodiments are not limited to the precise construction and components disclosed herein. Various modifications, changes and variations, which will be apparent to those skilled in the art, may be made in the arrangement, operation and details of the method and apparatus disclosed herein without departing from the spirit and scope defined in the appended claims. 

What is claimed is:
 1. A computer-implemented method comprising: receiving an indication, from a client device, of one or more map points of interest; identifying, based on the received indication, pre-fetch map data; determining a budget for storing the pre-fetch map data at the client device; receiving a request for the pre-fetch map data corresponding to one or more map points of interest; determining a change in availability of client device memory or network bandwidth; in response to determining the change in availability of memory or network bandwidth, dynamically-adjusting the budget for storing the pre-fetch map data at the client device; and determining if the request for the pre-fetch map data meets the tile budget; when the tile budget has not been met, sending pre-fetch map data until the budget is met or until all pre-fetch map data corresponding to the one or more map points of interest have been received at the client device; and storing the received pre-fetch map data in a local memory on the client device until a subsequent user request.
 2. The computer-implemented method of claim 1, wherein dynamically adjusting the budget comprises: dynamically adjusting the budget based on an amount of map data memory available during receipt of the pre-fetch map data and setting the budget at or below the amount of map data memory available.
 3. The computer-implemented of claim 2, wherein the memory is a general memory for the client device.
 4. The computer-implemented of claim 2, wherein the memory is a map data specific memory for the client device.
 5. The computer-implemented of claim 2, wherein dynamically adjusting the budget further comprises: updating a memory usage profile for the client device; and adjusting the budget based on the updated memory usage profile.
 6. The computer-implemented of claim 1, wherein dynamically adjusting the budget comprises: dynamically adjusting the budget based on an available number of map memory slots on the client device for storing the pre-fetch map data.
 7. The computer-implemented of claim 6, the method further comprising: determining an available amount of map data memory allocated for the client device to store the pre-fetch map data; accessing a memory allocation size for the map data; and determining the number of map memory slots in the available amount of map data memory.
 8. The computer-implemented of claim 1, the method comprising: receiving, at the client device, the pre-fetch map data in a sequential manner; and in response to receiving each pre-fetch map data, determining, at the client device, if the budget has been met.
 9. The computer-implemented of claim 1, the method comprising: identifying a plurality of the map points of interest each corresponding to a portion of the pre-fetch map data; and prioritizing the plurality of the map points of interest in an order from highest to lowest, such that requesting the pre-fetch map data comprises requesting the pre-fetch map data in order from highest to lowest corresponding to plurality of map points of interest.
 10. The computer-implemented of claim 1, further comprising identifying, from a plurality of zoom levels, one or more zoom levels, such that the pre-fetch map data are identified based on the one or more map points of interest and the identified one or more zoom levels.
 11. The computer-implemented of claim 10, further comprising storing map data at different zoom levels, the map data at each zoom level containing a respective set of pre-fetch map data tiles.
 12. The computer-implemented of claim 11, wherein the map data at each zoom level contains pre-fetch map data having a same memory allocation size.
 13. The computer-implemented of claim 1, the method further comprising awaiting a user interaction with the client device before identifying a subset of the pre-fetch map data stored on the client device and rendering the visual display using the subset of the pre-fetch map data.
 14. A non-transitory computer-readable memory storing instructions, the instructions when executed by a processor cause the processor to: receive an indication, from a client device, of one or more map points of interest; identify, based on the received indication, pre-fetch map data; determine a budget for storing the pre-fetch map data at the client device; receive a request for the pre-fetch map data corresponding to one or more map points of interest; determine a change in availability of client device memory or network bandwidth; in response to determining the change in availability of memory or network bandwidth, dynamically adjust the budget for storing the pre-fetch map data at the client device; and determine if the request for the pre-fetch map data meets the tile budget; when the tile budget has not been met, send pre-fetch map data to the client device until the budget is met or until all pre-fetch map data corresponding to the one or more map points of interest have been received at the client device; and store the received pre-fetch map data in a local memory on the client device until a subsequent user request.
 15. The non-transitory computer-readable memory of claim 14, wherein the instruction to dynamically adjust the budget for storing the pre-fetch map data at the client device comprises an instruction to dynamically adjust the budget based on an amount of map data memory available during receipt of the pre-fetch map data and an instruction to set the budget at or below the amount of map data memory available, wherein the map data memory is either a general memory for the client device or a map data specific memory for the client device.
 16. The non-transitory computer-readable memory of claim 15, wherein the instruction to dynamically adjust the budget based on an amount of map data memory available during receipt of the pre-fetch map data further comprises instructions to: update a memory usage profile for the client device; and adjust the budget based on the updated memory usage profile.
 17. The non-transitory computer-readable memory of claim 15, wherein the instruction to dynamically adjust the budget based on an amount of map data memory available during receipt of the pre-fetch map data further comprises instructions to: determine an available amount of map data memory allocated for the client device to store the pre-fetch map data; access a memory allocation size for the map data; and determine the number of map memory slots in the available amount of map data memory.
 18. A computer system for fetching map tile data to be used in constructing a visual display of map data on a client device, the computer system comprising: one or more processors of a computer system; and one or more memories of the computer system storing a plurality of modules including instructions for execution on the one or more processors, the modules including: a display module including instructions executed on the one or more processors to cause the computer system to construct and display the visual display of the map data; a map point identifier module including instructions executed on the one or more processors to cause the computer system to identify one or more map points of interest that define pre-fetch map data that are requested from a remote map database and stored on the computer system for eventual rendering of a visual display of map data in response to a subsequent user request; a database interface module including instructions executed on the one or more processors to cause the computer system to request, from the map database, the pre-fetch map data from the remote map database and to receive the pre-fetch map data from the remote map database; and a budget module including instructions executed on the one or more processors to cause the computer system to: determine a change in availability, at the computer system, of memory or network bandwidth; in response to determining the change in availability of memory or network bandwidth, dynamically adjust a budget for storing the pre-fetch map data and determine if the budget has been met by the received pre-fetch map data tiles; and when the tile budget has not been met, the map data interface module receives additional pre-fetch map data until the tile budget is met or until all pre-fetch map data corresponding to the one or more map points of interest have been received at the client device.
 19. The computer system of claim 18, wherein the instruction to dynamically adjust the budget for storing the pre-fetch map data further includes instructions to: update a memory usage profile for the client device; and adjust the budget based on the updated memory usage profile.
 20. The computer system of claim 18, wherein the instruction to dynamically adjust the budget for storing the pre-fetch map data further includes instructions to: determine an available amount of map data memory allocated for the client device to store the pre-fetch map data; access a memory allocation size for the map data; and determine the number of map memory slots in the available amount of map data memory. 